Composite structures are used in a wide variety of applications. In aircraft construction, composites are used in increasing quantities to form the fuselage, wings, tail section, and other components. For example, the wings of an aircraft may be constructed of composite wing skins with composite stiffening elements such as stringers extending in a spanwise direction along the wing skins. The stringers may be bonded to the wing skins to increase the bending strength and stiffness of the wing skins.
Stringers may be provided in a wide variety of cross-sectional shapes. For example, a stringer may be provided as a hat stringer having a hat-shaped cross-section including a base portion and a pair of webs extending from the base portion. The base portion may include a pair of flanges for coupling (e.g., bonding) to a skin member such as a wing skin. A stringer may also be provided as a blade stringer having a T-shaped cross-section and which may be formed by assembling a pair of L-shaped stringer halves. Each L-shaped stringer half may have a flange and a web. The webs of a pair of L-shaped stringer halves may be bonded together in back-to-back relation to form the blade stringer. The flanges of the blade stringer may be bonded to a skin member such as a wing skin.
Composite stringers may be formed by laying up a plurality of composite plies over a mandrel or form tool having the final shape of the stringer. After layup is complete, heat and/or pressure may be applied to cure the composite plies. Current methods of laying up individual composite plies over a form tool are performed manually or by machine. Manual layup is a time-consuming process requiring a large number of personnel performing a large amount of touch labor to layup multiple composite plies. The amount of touch labor may be significant for large-scale structures and high production rates. Machines such as automated tape-laying (ATL) machines may reduce the amount of touch labor for laying up composite structure. However, ATL machines are typically large and complex and may be prohibitively expensive for the total quantity of ATL machines that would be required to support a large-scale production program. In addition, ATL machines may require a large amount of machine path programming which may impact production cost and schedule.
As can be seen, there exists a need in the art for a system and method for laying up composite plies on a form tool with minimal touch labor and in an efficient and cost-effective manner.